Correcting circuit for ocean-cable relays



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J. w. MILNOR CORRECTING CIRCUIT FOR OCEAN CABLE RELAYS 4Sheets-Sheet 4 Filed Novv 9, 1927 Patented June 11, 1929.

JOSEPH W. MILNOR, OF MAPLEWOOD, NEW JERSEY, ASSIGNOR TO THE WESTERN UNION TELEGRAPH COMPANY, OF NEW YORK, N. Y. A CORPORATION OF NEW YORK.

CORRECTING CIRCUIT FOR OCEAN-CABLE RELAYS.

Application filed November 9, 1927.

My invention. relates specifically to an improvement in correcting circuits, particularly for ocean cable relays.

In its broad aspect, my invention covers means providing for the proper actuationoli a receiving or repeating relay upon receipt of current which has, during transmission, been so distorted by the character of, or conditions existing in, the transmission medium, or by apparatus connected thereto, that it has assumed a shape unsuitable to cfl'ect proper operation of the relay unless correction is provided. The invention covers a method of controlling and regulating the extent of correction efl'ected; this control is provided in one form of the invention, by the automatic closing, during each received impulse, of the supply conductor leadingv from a current source to the correcting net work and the automatic opening of a branch of the network at a definite time interval thereafter.

It is the purpose of the invent-ion to stabilize the action of the correcting circuit by permitting the current supplied into the correcting circuit to flow for a definite and constant length of time during each received signal, this length of time being independent of the strength or length of the signal as received from the cable. Thus each signal will have the same effect upon the correcting circuit.

This object can readily be accomplished in .a regenerative type of cable receiver or repeater by having the correcting current supplied from the outgoing circuit of the receiver or repeater. Correction of the signals by the correcting current thus derived may be effected either in the relay or in the amplifier. The signals transmitted by a regenerative repeater are of uniform length and amplitude irrespective of the signals received by the repeater. It is obvious, therefore, that a correcting system under the control of the outgoing circuit of a regenerative repeater can readilybe made to produce the desired uniformity of the correcting current.

The invention will be more readily understood from a consideration of the following description and the annexed drawings, in which:

Figs. 1 and 2 represent diagrammatically systems in which distortions, of the type referred to, are ordinarily produced, and to Serial No. 232,090.

which the correcting means of my invention may be applied;

Fig. 3 shows a common method of obtaining the necessary correction by the use of an auxiliary coil on the receiving relay to which correcting current of regulated magnitude and shape is supplied, for the purpose of correcting for a wandering zero Fig. 4 shows diagrammatically one means for applying the method of my invention to a circuit of the type shown in Fig. 3;

Fig. 5 represents the improved circuit of my invention in a regenerative type of cable receiver or repeater;

Fig. 6 is a theoretical diagram showing the signal current as sent from the transmitting end of the cable, and as received at the opposite end of the cable, together with the correcting current which must be produced at the receiving end in order that its clfect may be combined with the effect of the received current, to produce a resultant effect that will correct for wandering Zero Fig. 7 illustrates the application of my invention to a synchronous telegraph system in which the terminal or repeating set supplies locally signal elements which are not received with sufficient strength to operate the receiving relay;

Fig. 8 shows the application of the correcting means of my invention to the input of an amplifier or magnifier instead of applying it to the main receiving relay;

Fig. 9 shows diagrammatically the application of my correcting means to an amplifier, of the well-known Heurtley type.

It is customary to use condensers at the sending and receiving ends of a cable circuit, in order to eliminate earth currents.

. This is illustrated in Fig. 1, which is a diagrammatic showing of a usual form of cable circuit, in which 1 represents the cable, balanced at each end by artificial cable 2, 2, to provide for duplex operation. The transmitter 3 is, in the usual way, connected to the real and artificial cables through block condensers 4, 4, receiver 4 being connected across the outer terminals of the block'condensers. At the opposite end of the cable the receiver 4: is indicated as comprising any desired terminal apparatus, such as a mag nifier of any type, but it is obvious that the magnifier may be omitted and the cable terminals connected directly to the coil 5 of the receiving relay. The block condensers cause distortion of the cable signals for the 0f the vacuum tube type, with its input circuit coupled inductively to the cable circuit by a transformer 6, and its output circuit coupled to the coil 5 by a transformer 8.

Since the circuit of Fig. 3 may be more readily explained by referring to the curves of Fig. 6, reference is had first to this latter figure. In Fig. (3, if the curve marked ((1) represents the signals as sent from the transmitting end of the cable, the current in the receiving relay is approximately of the form shown by curve (6). It will be seen that the original signal (a) is indicated being made up of two short positive impulses of block form followed by a prolonged positive and-a short negative impulse. At the receiving end, the current has the same general contour so far as the relative lengths and polarities of the impulses are concerned, but it will be apparent from curve (6) that the normally horizontal line of zero current has in effect been curved and displaced downward, indicating the existence of the phenomenoncommonlycalled wandering zero. The effect of this distortion of received current on the receiving relayis such as to prevent its proper actuation. It is therefore necessary that a correction be applied, either to the relay or to the amplifier, simultaneously with the received current, and of such nature that the combined effect of the received current and the correction current is substantially the same asthat of a signaling current free from wandering Zero.

The curve (0?) in Fig.6 represents a current of proper shape .to actuate the relay, thiscurve having the same general contour as curve (a) and (b) so far as the occur rence of peaks is concerned, and also having a horizontal line of zero current. In order to produce a current represented by curve (d) it is necessary to combine with thev received current represented by curve (1)), a correcting current represented by curve (0), so that the algebraic sum of curves (2)) and (0) shall equal curve (d).

Fig.3 shows one common means for obtaining a correcting current, such as that illustrated by curve (a) of Fig. 6. In Fig. 3, 5 represents the main coil of the receiving relay 10 of a system such as that illustrated in either-Fig. 1 or Fig. 2. The received current in coil 5 is so distorted as to be incapable of properly actuating the relay 10. Anauxiliary coil 9 is ordinarily wound on a single rectangular form which-is suspended by fine wires between the poles of a strong magnet. The main vand auxiliary coilsof the relay, together with the tongue are mechanically connected so that all move together. The tongue 11 makes contact with one pole or the other of a split battery 12 to the midpoint of which a conductor 13 is connected. Auxiliary relays 14,-, 1 1 for operating the local apparatus are connected between the parts of the split battery 12 and the contacts 15, 1G cooperating with tongue 11. A conductor 17 is connected to the'tongue l1 and completes the circuit from the battery 12 by way of resistances 18, 18 and inductances 19, 19, the function of the resistances and inductanccs being to time and shape the current flow in the auxiliary coil of the main relay.

The difficulty with the method shown in Fig. 3 is that the arrangement is somewhat unstable. Thus, if one received current pulse is slightly too strong, it increases the length of time that current is applied to the correcting circuit, thus tending to cause the succeeding signals to be somewhat too strong. If, on the other hand, a received signal is too weak, current is applied to thecorrecting circuit for too short a time, thus causing the correcting current to be too weak, and the following signals tend also to be too weak. Any slight errors in adjustment of the system tend to cause an unstable condition which exaggerates the effect of wrong adjustment.

The solution for this problem lies in limiting the flow of correcting current independently of the strength or length of the signal as received from the cable. An arrangement for accomplishing this is illustrated in Fig. 4. In this ligure, the same numerals repre sent the same elements, as in Fig. The numeral 20 represents the tongue of a relay actuated by means not shown, the tongue being closed for a brief interval, each inter val of equal duration, at the center of each received signal. The relay may also be closed at the center of each space between signals, although this is not essential. The relay must be driven synchronously with the -received signals; it may in fact be driven from an auxiliary brush of a regenerative receiver or repeater in a manner generally similar to that illustrated in Fig. 5. The current sent into the correcting circuit, i. e., the current through the relay tongue 20 (Fig. 4-), is then as shown in curve (a) of Fig. (i, being made up of a series of impulses of equal duration occurring one to each re ceived signal and changing in polarity with change in polarity of the received signals. By the current limiting and retarding action of the resistances and inductances of the cor recting network, the current -which flows in the auxiliary coil 9 of the main relay 10 is shaped to be similar to the current represented by curve (0) in Fig. 6. The. resultant effect, therefore, of the received and correcting currents in the main and auxiliary coils of the relay is that which would be produced by a current having the form shown by curve in Fig. 6. lVith the arrangement as thus described, however, there is no danger of applying a too great correcting current for an unduly strong signal, because each received signal regardless of its strength, will have exactly the same effect in sending current into the correcting circuit.

In Fig. 5, which shows the invention applied to a regenerative receiver or repeater, the automatic interruption produced in Fig. 4 by the relay tongue 20, is accoi'iiiplished by the brush of a ring C of a commutator the brushes of which are moved uniformly in synchronism with incoming signals, being driven by means not shown. In this figure the solid rings and segments of the commutator, are, for the sake of simplicity, shown in development.

The operation of the system of Fig. 5 may be explained as follows \Vhcn a signal impulse is received in coil 5 of cable relay 10, the relay coils and tongue 11, being mechanically connected'to move in unison, are swung so as to cause the tongue 11 to establish a connection with either contact 15 or contact 16, depending upon the polarity of the received signal. A path is completed from battery 12 through tongue 11 to the solid ring 21 of the commutator and, as the rotating brush 22 moves onto one of the segments 23, current flows either through polar relays 24 and 25, or 26 and 27 by way of conductors 33 and 43 thereby causing the armature of either the plus or minus relay, depending upon the polarity of the received signal, to move against its front or marking contact. The armatures of these relays are normally biased against their spacing contacts s by current flow from source 28 through resistance 29 and the biasing coils3O of the several relays. The flow of current through this, uninterrupted circuit is relatively small; as will become apparent hereinafter, this flow may be momentarily increased by the short circuiting of resistance 29 upon the establishment of a shunt path thereabout by way of a segment of ring B.

.The armature of either the plus or minus relay 24: or 25 having been moved against its front contact, in the condition of the circuit shown in Fig. 5, the armature will be moves onto one of the segments 35, thereby closing a circuit from battery 31 or 31 through the tongue of the locked relay 24 or "25 and conductor 36 to the local apparatus; or to another cable or line through conductor 37. Assuming this to be a repeater station, the regenerated signal is thereupon transmitted to the output circuit of the repeater. At the same time the brush 34: of ring C closes a circuit through the correcting coils and resistances18, 19 by way of auxiliary coil 9 of main relay 10, this circuit being completed through ground at G and G and source 31 or 31*. As soon as the brush 34 leaves said segment 35, the correction circuit, as well as the outgoing circuit, is interrupted, the interruption being automatically effected by the commutator for each received signal and being independent, therefore, of the strength or length of the received'signal. The correction network 18, 19 supplies to the auxiliary coil a current having the proper time and shape to correct for the distortion of the received signal.

An instant after brush 34 passes from said segment 35, the brush 38 of ring B-moves onto a segment 39 and closes a circuit from current source 28through biasing coils 30 byway of the shunt path around resistance 29 already-referred tof The effect of this is a momentary increase in the strength of the biasing current sufficient to cause restoration of the displaced armature to its normal spacing contact. The magnitudes of the various relay currents are in the following order: operating current, increased biasing current, locking current, normal biasing current, the operating current being the largest.

It will be obvious that the brush 22 by making contact alternately with conductors 40 and 41 leading to relays .2 1- and 25, and to relays 26 and 27 respectively, causes operation of one or the other of each pair of plus and minus relays, taking the pairs alternately, and that the signals thus set up are retransmitted alternately to conductors 37 upon the establishment of the corresponding alternating connections from the armatures of the operated relay of each pair by way of brush 3 1 in the outgoing circuit.

If the signaling speed over a cable is increased beyond a certain value, a single dot impulse will not be received with sufficient strength or amplitude to operate the tre cciving relay. hen, however, a single impulse is followed by one or more impulses of the same polarity, the energy received will be sufiicient .to operate the relay. By supplying the missing signal elements :locally, it is possible to operate the cable at the increased speed.

In Fig. 7, I have shown my method of correction applied to a synchronous telegraph system in which the missing signal elements.

are supplied locally by, means ofa socalled synchronous vibrating circuit, comprising two polar relays and two segmented distributor rings.

The operation of the arrangement shown in Fig. 7 will beobvious to engineers from the previous. description of my correction method in connection with Fig. 5. NVhen no signals are received of suflicient strength or intensity, to operate the main relay 10, the polar relay 50 operates its armature 51, betweenits positive and negative contacts in synchronism with the movement of the brushes 53 and 54 over the segments of the distributor rings, thereby impressing alternating impulsesover the conductor 56 to the solid receiving ring 57,.which are in turn transmitted to the output circuit through the segmented ring as the brush traverses the segments 58. The output circuit is here represented by the coils S S which may be the selecting magnets of a printer or other receiving device. In case. of a repeater, however, S to S may be the operating windings of storing or looking relays of the repeater which setup the signals to be retransmitted by a transmitting distributor as is well known. hen the signal received over the cable is of sufficient strength, the relay l0 isactuated thereby and controls the polarity of the signal transmitted to the output. circuit through the. receiving rings of the distributor.

In one method of applying my correction method to the circuitarrangement shown in Fig. 7, the input of the correction circuit is shunted around a resistance R, in the common battery return conductor 56, of the receiving ring output circuit, the switch 60 being in position to connect points .61 and 62. The correction impulses for the coil 9 of the. relay may be supplied from the receiving rings by providing an auxiliary segmented ring, indicated in dotted lines at 64,

the switch 60 being then moved to dotted line. position to connect points 61 and 65.

.Inaddition to the two methods last described, in the case of a repeater set, the

.correction impulses maybe taken from the output of the transmitting rings as shown in connection with Fig. 5.

-In the method herein disclosed uniform correction. is applied tothe receiving relay lregardless of Whether the received signals are strong enough to operate the relay; This is usually desirable. However, it' it is desired to use for the correction, only the signals which operate the relay, it is obvious that this. may be done with a suitable arrangement of distributor rings.

In Figures 4, 5 and 7, the correction is applied to the main or receiving relay by means of an auxiliary coil. .Under some conditions, it may be desirable to apply the vious that it is not limited to the correction of this form of distortion but may be applied generally to the control of the wave form of a correcting current, particularly where the generation of correcting current is under the control of the received distorted current and is, accordingly, subject to exaggeration of the effects of disturbing variations in the latter. It is also obvious that my invention is not limited to the particular types of systems disclosed by way of ex ample in the annexed drawings.

I claim:

1. A correcting circuit forocean cable relays olf the type comprising a main receiver coil and auxiliary corrector coil, including a source of correcting current and a correcting network and means for permitting current flow into the correcting circuit from,

said source for a definite and constant length ot time during each received signal.

2. A correcting circuit for ocean cable re--.

lays of the type comprising a main receiver COll and auxiliary corrector coil, including a source of correcting current and a correcting network, means controlled by said main. receiver COll for initiating current flow tromsaid source into the correct-ing circuit in response to a received signal and means for terminating said current flow at a de inite time interval thereafter independent of the length of the received signal.

3. A correcting system forocean cable relays of the type comprising a main receiver coil and auxiliary corrector coil, including a source of correcting current and a correcting circuit, means for establishing connection of said source to said correcting circuit synchronously, with the received signal impulses and means for disconnecting the current source at uniform time intervals thereafter independently of the strength of the received signal impulses.

4. A correcting circuitfor ocean cable resource into said correcting network and means controlled independently of said re.

ceived signals to terminate current flow into said network while permitting discharge from said network into the auxiliary corrector coil.

5. A repeater circuit for ocean cable relays of the type comprising a main receiver coil and auxiliary Corrector coil, including a source of current adapted to supply current for the repeating of received signals, a commutator interposed between the source and an outgoing circuit and a correcting circuit for said auxiliary corrector coil, with means under control of said commutator for establishing connection from said source to said auxiliary corrector coil.

6. In a cable relay a main receiver coil adapted to receive distorted signals and an auxiliary coil associated with said main receiver coil with means for supplying to said auxiliary coil a current so shaped as to counteract the distortion of said signals, means for closing the circuit of the auxiliary coil at a given point during each signal impulse and means for openingsaid circuit at a different point during each signal impulse.

7. The method of applying correcting current in a system operating on distorted received signal current which comprises initiating the flow of correcting current in response to each of the received signal impulses making up said distorted received signal current and limiting the flow of correcting current at a definite and constant time interval thereafter independently of the strength or length of the received signals.

8. The method of correcting for distortion in a cable system subject to wandering zero, which comprises timing and shaping a correcting current in a manner determined in accordance with a desired wave form in which the wandering zero has been re stored to normal, but independently of the strength and length of the received distorted signal current, and combining the effects of said correcting and received currents to produce an effect uninfluenced by wandering zero.

9. A repeater system for cable relays comprising a receiver relay and an outgoing circuit, and a connection between said outgoing circuit and said receiver relay comprising a correcting circuit for applying correcting currents to said receiver relay, a source of current, a commutator between said source and outgoing circuit, and means for driving the brush of the commutator synchronously with received signal impulses in said receiver relay whereby current is supplied intermittently to said outgoing circuit and said correcting circuit in synchronism with said received signal impulses.

10. A repeater system for cable relays comprising a receiver relay, a transmitter relay and an outgoing circuit, said receiver relay comprising a main receiver coil and an auxiliary correetor coil, a correcting circuit for said auxiliary coil designed to regulate the wave form of current supplied to said auxiliary coil, a source of current and a commutator and means under the joint control of said transmitter relay and said commutator for supplying current from said source to the outgoing circuit and to the correcting circuit for said auxiliary coil.

11. A repeater system for cable relays comprising a receiver relay having a main receiving coil and an auxiliary corrector coil, and a contact member movable with the coils of the receiver relay to prepare a path for the regenerative ,transmission of received signal impulses, a commutator arranged to complete a path for the regenerative transmission of received signal impulses, and means under control of the commutator for supplying current to said auxiliary corrector coil in synchronism wit-l1 the received and regenerated signal impulses.

12. The method of operating a regenerative type of cable repeater in which the re ceived distorted current in the receiver relay is in effect combined with a correcting current to eliminate the effects of wandering zero which comprises jointly controlling the duration and strength of the regenerated signals and of the correcting impulses to produce uniformity of the correcting current relays of the type comprising a main receiver coil and an auxiliary correction coil, a current amplifier or magnifier interposed in the circuit between the cable terminal. and the cable relay, a source of correcting current and a network comprising resistance and inductances designed to shape and time the current from said source to effect proper operation of said relay, said network being connected to the input of said amplifier, means under control of the received signals to permit current flow from said sources into said correcting network and means for disconnecting the current source at uniform time intervals thereafter independently of the strength of the received signals.

In testimony whereof I affix my signature.

JOSEPH W. MILNOR. 

